I have a 2003 Gmc sierra its the 5.3 liter. I bought it last year last time i checked it’s mpg it was getting 16 mpg while pulling a trailer. Now a year later i noticed I’m filing up more so i went and did a tune up, things changed fuel filter, oil, oil filter, spark plugs, spark plug wires, air filter, added fuel injector cleaner. I did this with my friend at his shop he owns and he didn’t notice anything else that needed to be changed. Well now I have been driving really thinking about conserving gas and just checked I’m getting 11.68 mpg. Is there something we are missing that could possibly be causing it to be this low. its a full stock gmc nothing modded not lifted no weight added and no codes or lights.
Thanks
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Filed under Gas Conservation FAQ by on Apr 25th, 2011. 6 Comments. 
I had a half tank of gas and traveled 79 miles and my gas tank was empty at that point. What would make the mpg change? I drove back roads and basically drove slower to conserve on gas. Instead my car gobbled it up. Average speed 50 mph.
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Filed under Gas Conservation FAQ by on Aug 26th, 2010. 2 Comments.
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